Date: Fri, 14 Oct 2005 12:34:55 -0400 (EDT) From: rick@snowhite.cis.uoguelph.ca To: fs@freebsd.org Subject: FreeBSD NFS server not responding to TCP SYN packets from Linux/SunOS clients Message-ID: <200510141634.MAA22435@snowhite.cis.uoguelph.ca>
next in thread | raw e-mail | index | archive | help
> ps: It would be nice if someone with the right expertise could explore > other things in TCP specifically for NFS. For example, I don't see > why a retransmit timeout should go above about 100msec > > nfs/rpc shouldn't retransmit at all over tcp except when there has been a > reconnect. Tcp might retransmit, but modern implementations will always > choose the right timeout dynamically, unless packet loss is excessive. > Yes, I was referring to TCP retransmits and I was suggesting that TCP might not be "choosing the right timeout dynamically". A lot of what is in TCP timers now dates back to work done w.r.t. congestion avoidance (very good work, I might add) in the late 1980s. I don't know if anyone has revisited this, now that almost everything is gigibit fibre (in the late 1980s, there were still 56Kbps internet links out there). I don't know enough about TCP (and haven't looked at recent literature), but I do know that I see retransmit timeouts back off to 1-2sec quite rapidly, as soon as I introduce a 20msec transit delay between client<->server and throw away the odd packet. The result is abismal NFS/TCP preformance. rick
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200510141634.MAA22435>